If you open the variable containing the the decompressed tar data as a ramfile (Search for  # in memory files in perlfunc (5.8.x)), you should be able to pass the resultant filehandle to Archive::Tar. Something like (untested):

...
my $uncompressed = memBunzip( $compressed );
open my $ramFH, '<', \$uncompressed;

my $tar = Archive::Tar->new;

my @ATFobjects = $tar->read( $ramFH, 0, { extract => 1 } );

for my $ATFobject ( @ATFObjects ) {
    my $content = $ATFObject->getContent;
    ## Do something with the content.
}
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